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DNA dan Replikasi

DNA dan Replikasi. History. R strain could become virulent when it took in DNA from heat-killed S strain. Experimen dg Streptococcus pneumonia galur : Smooth (S) – Virulent (gel coat) Rough (R) – Kurang Virulen. Structure. Phosphate Group. O=P-O O. 5. CH2. O.

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DNA dan Replikasi

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  1. DNA danReplikasi

  2. History

  3. R strain could become virulent when it took in DNA from heat-killed S strain Experimen dg Streptococcuspneumonia galur : Smooth (S) – Virulent (gel coat) Rough (R) –KurangVirulen

  4. Structure

  5. Phosphate Group O=P-O O 5 CH2 O N Nitrogenous base (A, G, C, or T) C1 C4 Sugar (deoxyribose) C3 C2 DNA Nucleotide O

  6. Deoksiadenosinmonofosfat Deoksiguanosinmonofosfat

  7. Deoksi timidin monofosfat Deoksisitidinmonofosfat

  8. Melting and Renaturation of DNA Renaturation driven by homologous base pairing Will also hybridize with a radiolabeled 5’-ACGGCTA-3’ “probe”.

  9. Senyawa yang menstabilkan kondisi terdenaturasi O O NH2  C  NH2 NH2  C  H Urea Formamid

  10. Replication

  11. Replication • Process of duplication of the entire genome prior to cell division • In eukaryotes , replication only occurs during the S phase of the cell cycle.

  12. Synthesis Phase (S phase) S phase DNA replication takes place in the S phase. G1 G2 interphase Mitosis -prophase -metaphase -anaphase -telophase • S phase during interphase of the cell cycle • Nucleus of eukaryotes

  13. DNA replication occurs with great fidelity (New cells will need identical DNA strands)) Somatic cell DNA stability and reproductive-cell DNA stability are essential. Why? Identity Pan troglodytes 98.77% sequence identity Genetic diseases

  14. Basic rules of replication • Semi-conservative • Starts at the ‘origin’ • Bidirectional • Semi-discontinuous • Synthesis always in the 5-3’ direction • RNA primers required

  15. DNA replication Of the 3 possible models, replication is… A) Semi-conservative Meselson-Stahl experiments

  16. B) Starts at origin Initiator proteins identify specific base sequences on DNA called sites of origin Prokaryotes – single origin site E.gE.coli - oriC Eukaryotes – multiple sites of origin (replicator) E.g. yeast - ARS (autonomously replicating sequences) Prokaryotes Eukaryotes

  17. Bidirectional replication of circular DNA molecules.

  18. Temporal ordering of DNA replication initiation events in replication units of eukaryotic chromosomes.

  19. C) bidirectional • Replication forks move in one or opposite directions

  20. D) Semi-discontinuous replication Anti parallel strands replicated simultaneously • Leading strand synthesis continuously in 5’– 3’ • Lagging strand synthesis in fragments in 5’-3’

  21. E) Synthesis is ALWAYS in the 5’-3’ direction Nucleotide recognition Enzyme catalysed polymerisation (DNA polymerase) Complementary base pair copied Substrate used is dNTP

  22. F) RNA primers required • DNA polymerase can only join an incoming nucleotide to one that is base-paired • RNA primase provides a base paired 3’ end as a starting point for DNA pol by synthesising ~10 nucleotide primers

  23. Animasireplikasi

  24. EnzimdalamReplikasi DNA exonuclease3’-5’ exonuclease5’-3’ SSB (ssDNA binding protein) Binds to and stabilizes ssDNA

  25. What happens if a base mismatch occurs? Where does energy for addition of nucleotide come from? From cleavage of high energy phosphate of incoming triphosphate DNA polymerase has 3’  5’ exonuclease activity in order to correct errors

  26. Why does DNA replication only occur in the 5’ to 3’ direction?

  27. DNase I DNase II Exonuclease

  28. Replication of the ends of linear DNA newly synthesized DNA RNA primer 3' 5' template Since all known DNA polymerases need a primer, how are the ends of linear DNA replicated in eukaryotes?

  29. Example GGGGTT GGGGTT GGGGTT (GGGGTT)n n = 20 - 200 Telomeres repetitive DNA at the end of linear eukaryotic chromosomes 5'

  30. AACCCCAAC telomerase Telomerases: enzymes that add DNA repeats to the 3' end of DNA. Telomerases are composed of protein and an RNA molecule that functions as the template for telomere synthesis.

  31. Human telomerase Responsible for maintaining telomere length in eukaryotic chromosomes Main components: Telomerase reverse transcriptase Human telomerase RNA (hTR) Reverse transcriptase Transcribes RNA to DNA (rather than the usual DNA to RNA) hTR is the template for the repeated region

  32. GGGGTT 5' AACCCCAAC GGGGTT 5' telomerase

  33. AACCCCAAC GGGGTT GGGGTT GGGGTT GGGGTT GGGGTT GGGGTT 5' primase 5'

  34. pol III 5' pol I ligase telomeric repeats

  35. For most cells, telomeres are added during development. Later telomerase becomes inactive. Hence, as cells divide the DNA becomes shorter. Note that telomerase is reactivated in many types of cancer cells.

  36. OBAT anti REPLIKASI DNA

  37. INHIBITOR TOPOISOMERASE (Gyrase) Antibiotik QUINOLON : MENGHAMBAT TOPOISOMERASE BAKTERI GRAM NEGATIF, MODIFIKASI BAKTERI GRAM POSITIF DAN AEROBIK Camptothecin : INHIBITOR TOPOISOMERASE I SEBAGAI ANTI KANKER DENGAN MENSTABILKAN BENTUK ENZIM TERIKAT PADA DNA SECARA KOVALEN

  38. TOPOISOMERASE SBG TARGET OBAT Novobiocin – subunit ATPase GyrB Asamnaladiksat – Gyr A Ciprofloxacin (oral) – stop replikasi MENGGANGU PROSES PEMOTONGAN DAN PENYAMBUNGAN UNTAI DNA

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